Performance on Contaminated Runways

7/29/2019 Performance on Contaminated Runways

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Performance oncontaminated runways

-Friction Coefficient - Crosswind - Use of FCOM

Operations Liaison Meeting


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2Performance on contaminated runways - Friction coefficient - Crosswind - Use of FCOM

Content

Runway condition: Airport information Correlation airport information/FCOM data

FCOM data

Performance determination

Crosswind

Conclusion


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A SNOWTAM contains :

The type of contaminants,

Mean depth for each third of the runway length,

Estimated braking action,

Reported Mu ()(Friction coefficient)

Reported Mu Estimated

Braking Action

0.4 and above GOOD

0.39 to 0.36MEDIUM/GOOD

0.35 to 0.30 MEDIUM

0.29 to 0.26

MEDIUM/POOR

0.25 and below POOR

Runway condition: Airport information


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Airbus charts are provided by type of contaminants

and the depth of contaminant on the runway.1/4 and 1/2 inch of slush, 1/4 and 1/2 inch of water, compacted snow

A linear relation has been established between loose snow and slush,

Sometimes, only the Estimated braking action orReported Mu is available.

Is it possible to get the performance from a given reported Mu?

Runway condition: Airport information


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Airports release a friction coefficient derived from

a measuring vehicle. This friction coefficient is

termed as reported Mu

The actual friction coefficient, termed as effectiveMu (or aircraft Mu) is the result of the interaction

tire/runway.

It depends on the tire pressure, tire wear, aircraftspeed, aircraft weight and anti-skid system efficiency.

Correlation airport information/FCOM dataEffective mu and reported mu


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Measuring vehicles operate at much smaller weight

and speed than aircraft.

Tests have demonstrated that there is a poor

correlationbetween the reported Mu and theeffective Mu. There is even a poor correlation in

between the measuring vehicles.

Even with an ideal reported Mu equals to the

Effective Mu the type and depth of contaminants

would be necessary.

Correlation airport information/FCOM dataEffective mu and reported mu


7/507Performance on contaminated runways - Friction coefficient - Crosswind - Use of FCOM

There is a clearseparation in the effect of contaminants on

the aircraft performance in hard and fluid contaminants

Hard contaminants are : Compacted snow and ice

Fluid contaminants are : Water, slush and loose snow.

Hard: Decrease of friction forces

Fluid: Decrease of friction forces +

precipitation drag and aquaplaning

Correlation airport information/FCOM dataHard and fluid contaminants



Precipitation drag The precipitation drag is composed of : Displacement drag

produced by the displacement of the contaminant fluid from the path of

the tire.

Spray impingement drag

produced by the spray thrown up by the wheels (mainly those of thenose gear) onto the fuselage.

The effect of these additional drags must be

accounted for:

They affect the deceleration performance: positive effect.

They affect the acceleration performance: negative effect.

The effect on the acceleration leads to a limitation

in the depth of fluid contaminants on the runway.

Correlation airport information/FCOM data



Aquaplaning The presence of a fluid contaminant on the runway creates

an intervening film between the tire and the runway

leading to a reduction of the dry contact area.

It gets more critical at higher speeds where the fluid

cannot be squeezed out from between the tire and therunway.

Aquaplaning is a situation where the tire of the aircraft are

to a large extend separated from the runway surface.

Friction forces drop to almost negligible values.

Directional control and braking are virtually

ineffective.

Correlation airport information/FCOM data



Airbus does not provide the take-off and landingperformance on contaminated runways according to

the reported braking action or to a reported .

Aircraft performance on a fluid contaminated runway

depends on the effective and the depth of fluid onthe runway.

Charts are provided for: 1/4 inch water, 1/2 inch water, 1/4 inch slush, 1/2 inch slush.

Aircraft performance on a hard contaminated runwaydepends on the effective .Charts are provided for: compacted snow (=0.2) and icy runway (=0.05)

Correlation airport information/FCOM dataSummary



FCOM data

Runway Conditions:

Dry / Damp

Wet

Contaminated

Different Contaminants:

Standing Water

Slush

Wet Snow

Dry Snow

Compacted Snow



FCOM data



FCOM data

Standing water:

3 mm: wet

> 3 mm: contaminated

Different Contaminants - Standing Water



FCOM dataDifferent Contaminants - Slush

Slush:

2 mm: wet> 2 mm: contaminated



FCOM dataDifferent Contaminants - Wet snow

Wet snow:




FCOM dataDifferent Contaminants - Dry snow

Dry snow:



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WET or CONTAMINATED?

15 mm: wet

4 mm: wet 2 mm: wet 3 mm: wet

Dry SnowWet SnowSlushStanding Water

FCOM dataDifferent Contaminants - Summary


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In case of a wet

runway use:

WET runway corrections

FCOM data


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In case of a contami-

nated runway: Standing Water > 3 mm:

depth 3 mm ~ 6.3 mm

depth 6.3 mm ~ 12.7 mm

Slush > 2 mm:

depth 2 mm ~ 6.3 mm

depth 6.3 mm ~ 12.7 mm

FCOM data


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In case of a contaminated runway:

Wet Snow > 4 mm:

12.7 mm (1/2 inch) wet snow isequivalent to 6.3 mm (1/4 inch)

slush.

Dry Snow > 15 mm:50.8 mm (2 inches) dry snow is

equivalent to 6.3 mm (1/4 inch)

slush.

Compacted Snow:

12.7 mm6.3 mm=

Wet Snow Slush

50.8 mm

6.3 mm=

Dry Snow Slush

FCOM data


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15 mm

4 mm2 mm3 mm


any depth

Compacted Snow

12.7 mm 12.7 mm

25.4 mm

6.3 mm 6.3 mm

12.7 mm

50.8 mm

Wet runway corrections

15 mm

4 mm2 mm3 mm

FCOM data - Summary


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any depth

Compacted Snow

12.7 mm

25.4 mm

6.3 mm

12.7 mm

50.8 mm

15 mm

4 mm2 mm3 mm

Contaminated

runway corrections

12.7 mm

6.3 mm

FCOM data - Summary


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any depth

Compacted Snow

12.7 mm 12.7 mm

25.4 mm

6.3 mm

15 mm

4 mm2 mm3 mm

Contaminated

runway corrections

6.3 mm

12.7 mm

50.8 mm

FCOM data - Summary


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any depth

Compacted Snow

12.7 mm

6.3 mm 6.3 mm

12.7 mm

50.8 mm

15 mm

4 mm2 mm3 mm

12.7 mm

25.4 mm

Contaminatedrunway corrections

FCOM data - Summary


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Dry SnowWet SnowSlushStanding Water Compacted Snow

12.7 mm 12.7 mm

25.4 mm

6.3 mm 6.3 mm

12.7 mm

50.8 mm

15 mm

4 mm2 mm3 mm

Contaminatedrunway corrections

any depth

FCOM data - Summary


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any depth

Compacted Snow

12.7 mm 12.7 mm

25.4 mm

6.3 mm 6.3 mm

12.7 mm

50.8 mm

15 mm

4 mm2 mm3 mm

FCOM data - Summary


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Performance determination Landing: refer to FCOM tables

Takeoff: Different methods are available depending on each

airlines

The level of conservatism or details and difficulty

depends on the method

Takeoff chart DRY + FCOM correction

Takeoff chart DRY + takeoff chart correction(OCTOPUS: A319, A321, A330, A340)

Takeoff chart CONTAMINATED

Less Paper Cockpit program (LPC)


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FCOM:

Landing distances

Performance determination - Landing

For all runway conditions


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Takeoff chart DRY + FCOM correction

- Takeoff chart DRY

Performance determination - Takeoff


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Performance determination - TakeoffTakeoff chart DRY + FCOM correction

- FCOM corrections


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Performance determination - Takeoff Takeoff chart DRY + Takeoff chart correction


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Performance determination - Takeoff Takeoff chart CONTAMINATED


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Performance determination - Takeoff Less Paper Cockpit (LPC) program


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Airport : Airbus City, runway 31

OAT = 5oC, No wind, Standard QNH

Runway covered with 5 mm slush

Performance determination - TakeoffExample: A330-223


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245.9 3/6

159/62/67

Performance determination - TakeoffTakeoff chart DRY + FCOM correction

- Takeoff chart DRY


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Takeoff chart DRY +

FCOM correction- FCOM corrections


24.8

MTOW DRY 245.9Correction - 24.8

Corrected Weight 221.1


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MTOW DRY 245.9

Correction - 24.8Corrected Weight 221.1

Takeoff chart DRY +

FCOM correction- FCOM corrections


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Takeoff chart DRY+ Takeoff chart

correction

Performance determination - Takeoff245.9 3/6

159/62/67


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MTOWDRY

245.9

Correction - 23.2

MTOW1/4 SLUSH

222.7

Takeoff chart DRY+ Takeoff chart

correction


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225.0 3/3

142/52/55

Performance determination - TakeoffTakeoff chart CONTAMINATED (Slush 1/4)


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A330-223

Airport : Airbus City, runway 31

OAT = 5oC, No wind, Standard QNH

Runway covered with 5 mm slush


Takeoff chart

DRY + FCOM

correction

Takeoff chart

DRY + chart

correction

Takeoff chart

SLUSH(*)

LPC

program

221.1 t 222.7 t 225 t 225 t

Method

Takeoff

weight

Difficulty

of use

Summary

(*) If max TO weight SLUSH > max TO weight DRY, take max TO weight DRY


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CrosswindDemonstrated crosswind

A demonstrated crosswind is given in the FCOM Demonstrated : Maximum crosswind which was

experienced during the flight test campaign.

Applicable fordry and wet runways.

Demonstrated crosswind is not a limitation.

This is an information providing an indication of what

was experienced during flight test to give some

guidance for operators to establish their own

limitations.

FAR/JAR 25 requires this information to be given.


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Crosswind


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Crosswind on contaminated runways

A poor runway friction coefficient affects both

braking actionanddirectional control and thus

the capability to sustain high crosswinds fortakeoff and landing

Airbus has issued some recommendations based

on calculation and operational experience

Crosswind


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CrosswindCrosswind on

contaminatedrunways


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Conclusion On wet and contaminated runways it is mandatory

to get the type and depth of contaminant Reported runway friction coefficient (Mu) and estimated

braking action are of no use to determine takeoff and

landing performance

Several tools and methods exist to determinetakeoff performance

When operating regularly on contaminated

runways it is recommended to publish takeoff

charts for the associated contaminant

Documents

Performance on Contaminated Runways